Friday, 4 September 2009

Almost warp knitting fabric used Polyester and Nylon fiber for the raw material,following is the characteristics of Polyester and Nylon Fiber.

Polyester Fiber
Basic Principles of Polyester Fiber Production — The most common polyester for fiber purposes is poly (ethylene terephthalate), or simply PET. This is also the polymer used for many soft drink bottles and it is becoming increasingly common to recycle them after use by remelting the PET and extruding it as fiber. This saves valuable petroleum raw materials, reduces energy consumption, and eliminates solid waste sent to landfills.
PET is made by reacting ethylene glycol with either terephthalic acid or its methyl ester in the presence of an antimony catalyst. The reaction is carried out at high temperature and vacuum to achieve the high molecular weights need to form useful fibers. PET is melt spun. For a detailed production flowchart, go here.

o Most items made from polyester can be machine washed and dried. Use warm water and add a fabric softener to the final rinse cycle. Machine dry at a low temperature and remove articles as soon as the tumbling cycle is completed.
o If ironing is desired, use a moderately warm iron.
o Most items made from polyester can be dry-cleaned.

Nylon Fiber
Basic Principles of Nylon Fiber Production — The term nylon refers to a family of polymers called linear polyamides. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. Thus nylon 6,6 which is widely used for fibers is made from adipic acid and hexamethylene diamine. The two compounds form a salt, known as nylon salt, an exact 1:1 ratio of acid to base. This salt is then dried and heated under vacuum to eliminate water and form the polymer.

In another approach, a compound containing an amine at one end and an acid at the other is polymerized to form a chain with repeating units of (-NH-[CH2]n-CO-)x. If n=5, the nylon is referred to as nylon 6, another common form of this polymer. The commercial production of nylon 6 begins with caprolactam uses a ring-opening polymerization. For a detailed production flowchart, go here.

In both cases the polyamide is melt spun and drawn after cooling to give the desired properties for each intended use. Production of nylon industrial and carpet fibers begins with an aqueous solution of monomers and proceeds continuously through polymerization, spinning, drawing, or draw-texturing.

o Most items made from nylon can be machine washed and tumble dried at low temperatures. Use warm water and add a fabric softener to the final rinse cycle.
o Remove articles from dryer as soon as tumbling cycle is completed.
o If ironing is required, use warm iron.

Nylon 6,6 and Nylon 6 are the most versatile commercial nylon products in the market having a vast range of uses depending upon the need. Both the products are used for engineering applications though Nylon 6,6 is more used for its ductility and tensile strength. Nylon-6,6 which is also known as Polyamide 6,6.is the semi-crystalline polyamide commonly used in fiber applications such as carpeting, clothing, and tire cords. Nylon 6 which is also known as Poly-caprolactum has many individual uses. The numerical nomenclature for nylon is derived from the number of carbon atoms in the diamine and dibasic acid monomers used to manufacture it. The ratio of carbon atoms is what gives each nylon type its unique property characteristics.
Nylon 6 is used more for products like Bristles for toothbrushes, sutures for surgery, manufacture of hosiery, knitted garments. Also recently there had been more products developed using Nylon 6 which includes large variety of threads, ropes, filaments, nets, and tire cords.
Nylon 6,6 has a tighter molecular structure than nylon 6 due to a higher level of hydrogen bonding and maximum alignment between molecular chains, creating a tighter structure that better resists crushing, matting and stain penetration. Nylon 6 does not have this level of internal bonding, resulting in a more open structure. Nylon 6,6 gives carpet the unique balance of strength, elasticity and durability it needs to survive in commercial installations.
The stiffness of nylon 6/6 can be improved up to 10 times. The use of internal lubricants improves on the already excellent wear resistance and friction properties on nylon 6/6. Its versatility allows it to be used in almost any application that requires high physical strength, ductility, heat resistance and chemical resistance.